Daniel, this may be what you're after:
{#1, f[#2]} & @@@ data
On Tue, 20 Jan 2009, D. Grady wrote:
> Hi, suppose we've got a matrix
>
> data = {{a, b}, {c, d}};
>
> and we want to map a function onto just the second column, so we want
> to end up with
>
> {{a, f[b]}, {c, f[d]}}.
>
> The best way I've found to do this is with MapAt:
>
> MapAt[f, data, Table[{i, 2}, {i, Length@data}]]
>
> Is there a better way? I keep hoping there's some notation similar to
> what's used in Part that lets you refer to a whole column with All,
> like data[[All,2]]. Thanks!
>
> -Daniel
>
>